Niobium Sesquioxide, Nb₂O₃

Niobium Sesquioxide, Nb₂O₃, has been prepared (a) as a bluish-black powder by reducing niobium pentoxide with magnesium powder; the magnesium oxide so formed and excess of magnesium are removed with dilute hydrochloric acid; (b) as a bright grey powder with a bluish tinge by heating the pentoxide in a stream of hydrogen at 1250° C. The latter method yields a product which is free from both metal and higher oxides. The pure product melts at 1780° C. Its electrical conductivity has been measured. On being mixed with carbon and heated in hydrogen at 1200° C. it yields niobium carbide, NbC.